The lab cache tab has gone because you have zero lab caches. This is normal - the tab does not show if you have no lab cache finds (ditto challenge tab, hides, FTFs, etc). The problem is why has PGC lost their lab cache data? I suspect a change in the API, however it was working with the new API, so I think a repair to some other part (TB data?) broke lab cache data.
I had 51 lab caches and 12 types in a day :-(
It's all very sad....